Upon packaging large series of flat articles. The articles are formed into stacks of suitable size which are moved into the package. In these stacks, the articles are parallel, and the goal is to place them tightly against each other in the direction transverse to their planes. A typical example of articles of this kind is envelopes. The handling and packaging of envelopes is described e.g. in the Finnish Patent No. 94042 and in the Finnish published specification No. 97355 by the applicant.
Some articles have such a structure that the thickness of the article is not constant in the direction of its plane. A good example of such a product is envelopes and bag covers which are filled in from the short end, at which there is a closing flap and possibly also a paper covering the adhesive area on it, whereby the product is clearly thicker at one end. If the closing flap is folded out, it forms the thinnest end of the article. When articles of this kind are packaged with an automatic packaging apparatus, in which the articles run in a continuous stack, such constructional features cause more thickness at one end of the stack, which may hamper space utilization.